Field of the Invention
The present invention relates to the field of computer graphics and, in particular, to a system and method for temporal cadence perturbation for time-division stereoscopic displays.
Description of the Related Art
The illusion of depth in stereoscopic displays is created when at least two images are fused perceptually by a viewer in space and time during the act of viewing. The mechanics of display technologies and the need to isolate multiple image streams on a single display device often incurs time separation of the image streams (e.g., a single projector digital cinema or most 3D (three-dimensional) televisions). Accordingly, in the case of stereoscopic time division, the left image precedes the right image (or vice versa) by some sub-frame period.
Efforts to reduce the temporal separation of the image streams include “double flashing” or “triple flashing” the images such that for each image set (frame pair) the individual images are shown twice or three (or conceivably more) in an interleaved fashion (e.g., LRLRLR in 1/24 seconds for triple flash digital cinema). In order to project in 3D so that viewers do not suffer from any discomfort, the projector “flashes” each frame for each eye three times as fast as with conventional projection. This tripling of the frame rate (e.g., from 48 fps (frames per second) to 144 fps) smoothes the projection and provides for better motion rendition.
However, even with this “triple flash” technique, one image stream (e.g., the left eye image stream) precedes the other image stream by a fixed period. For example, in the LRLRLR example, the left image precedes the right image by 1/144 seconds every 1/24 seconds, or more precisely, the three exposures of each left image as a set, precede the three exposures of the set of right images by 1/144 seconds. Displaying one image or image set before the other image or image set of the pair causes unwanted “false depth” cues depending on the temporal separation of the image streams and the axis of motion of objects in the scene. False depth is the phenomenon that an object that is moving along the axis of ocular separation (e.g., left-to-right or right-to-left) appears to have an added depth component into or out of the screen, depending on which (left or right) image is shown first and possibly the polarity of the projector. The false depth is undesirable and can be jarring or uncomfortable to the viewer.
As the foregoing illustrates, there is a need in the art for an improved technique that addresses the limitations of current approaches set forth above.